The invention is concerned with fragrance cartridges for storing fragrances, and for releasing them on demand by means of a stream of carrier gas that may flow through the cartridges.
Odour presentation has typically been carried out using scent bottles and absorbent paper smelling strips, scent pens or olfactometers. These presentation methods suffer on the one hand from inaccurate dosing and the possibility of contamination of surfaces with liquid samples, and on the other hand from the complexity of the dosing device. Recently, fragrance cartridges have been proposed that can store fragrance for long periods of time before releasing the fragrance in a time-dependent and controlled manner by means of a flow of carrier gas.
Fragrance cartridges are known in FR 2771930. They are described as being capable of releasing fragrance on a stream of carrier gas in a time-controlled manner. A cartridge consists of a cylindrical reservoir of uniform cross section. The fragrance is contained in the reservoir and is supported on a suitable carrier material. Closure of the reservoir to prevent fragrance loss during storage is provided by flexible membrane disks that seal both ends of the reservoir. Fragrance is released when the membranes are punctured with hollow needles or cannulae, whereupon fragrance is permitted to flow out of the reservoir and through the needles or cannulae on a stream of carrier gas.
The prior art does not disclose any information as to the dimensional requirements of the cartridges needed to facilitate storage and release of fragrance from said cartridges. Storage and release is simply predicated on the puncture and re-sealing of the flexible membranes using cannulae. Whereas fragrance can be released in a satisfactory manner on a carrier gas stream from such cartridges by such measures, when gas flow is interrupted, fragrance continues to leak from the cannulae and strong fragrant head space around the cannulae can be detected. Whereas this evolution of unwanted head space can be remedied by removing the cannulae, the repetitive puncturing and removal inevitably compromises the sealing properties of the membranes, leading eventually to failure of sealing properties and leakage.
Furthermore, removal of cannulae requires a mechanical operation. If this is done by manual intervention, the process of switching from the emission of one fragrance accord to another is slow and laborious, rendering the cartridge impractical if rapid entry and re-entry into the reservoir is required to release fragrances in a responsive time-dependant manner. Yet, if automated means for this operation are provided, it adds to the complexity of the design of the cartridge, or means interacting with the cartridge thereby adding to the expense of achieving fragrance delivery.
There remains a need to provide fragrance cartridges that are capable of releasing fragrance material on demand and in a time-controlled manner on a stream of carrier gas, and yet when inactive, they are able to store fragrance essentially without leakage by employing means that are capable of mass-production at low cost.
A study of the diffusion behaviour of fragrances revealed that displacement per unit time of even very diffusive fragrance materials was, remarkably, rather small. It was also surprisingly found that if fragrance molecules were permitted to diffuse through narrow capillaries, even the most diffusive molecules were so constrained that the capillaries acted essentially as if they were closed. This allowed the development of a very simple means of actuating and interrupting flow of a fragrance from a fragrance-containing reservoir without the need for mechanical intervention to interrupt flow.